Multiple heater control



1,619,510 March 1 1927 H, A. HANDS MULTIPLE HEATER CONTROL Filed Deo. 30, 1926 b M @WKZ/JM 174% MM AW.

Y Patented Mar. 1,1927.

yUNI-TEDA STATES;

PATENT OFFICE.

'HOWARD' A. nANns, or WATEBTOWN, MASSACHUSETTS, Assrenon To HOOD RUBBER COMPANY, or WATERTOWN, MASSACHUSETTS, A .CORPORATION or MASSACHU- SITES.

irULTIrLE HEATER CONTROL. f

Application led December 30, 1926. Serial Nd. 158,004.

My present invention relates to improvements in means for regulating the temperature of a plurality ofelectric heaters and is in` the nature of amodification of the in- 6 vention disclosed by me in'a prior application led in the U. S. Patent Oilice on the u 17th day of June, '1926, Serial No. 116,652,

- electric couple of each heater -of means for varying oradjusting the amount of current induced therein by the `temperature variations in the heater. I-

In Order that the invention may be readily i understoodI' have appended hereto a sheet' of drawings in which the ligure is a diagrammatic view corresponding to Fig. 1 of my aforesaid application with the present invention incorporated therein.

Referring by reference characters to this drawing the numerals 76, 76, 76Pand 76 indicate the heaters; 35, 35", and 35 the corresponding thermo-electric elements or couples, electrically connected to the control 35 instrument so designated through the circuit controller 36 in a mannerwhich will be readily understood from the diagrammatic view in view of the specific description contained in my aforesaid application which it is deemed unnecessary to repeat here.

Included Ain the electric circuit of each thermo-couple 35, etc. is a variable resistance 135, 135, 135b and 135 which may be of any desired-type capable of adjustment to increase or diminish-the flow of current, the movable element of each being operativelyconnected with or operaterd by a pointera cooperating with a dial for indi-4 cating the setting of the resistance.

In use the control table of the control instrument would be set for a temperature approximately equal tothe average of all the temperatures `to be controlled. For example, if the foul` heaters had respectively temperature settmgs of 326, 330, 332 and 334 the control instrument would be set for about 330, which setting wouldbe incorrect for all but the second heater.

For the lirst heater 76 therefore the resistance 135 in its thermo-Couple circuit would be set for a 4lower .value than normal sol that a temperature of. 326 at the hot junction point wouldV cause as much current to flow through thegalvanometer as would a temperature of 330 if the rheostat. werel` at its normal setting. SimilarlyA the resistances in the last two heaters would be increased to decrease the effect at the instrument of the higher 'temperatures at their hot junctions.

Assuming a resistance ofthe instrument leads, and the rheostat in its normal position of 300 ohms, an instrument setting of 330, and an air temperature of 70 the current thru the galvanometer would be 33o-7o f soo K' when K is a constant depending onl the `millivoltage generated by thetype of couple used. Then 240 y Y v C=-0-K.8K.

dicate the number Of degrees above or below the instrument setting for which anycircuit 1s s et. B turning the dial to its normal position t e correct temperature could -be read when desired.

With such anv arrangement the contact table of the instrument will vnot be continuall moved from one lacetol another and w11, therefore, cause ess wear on the instrument than does the present method. The

- fact that the position of equilibrium4 for the galvanpmeter is always the same means that it will come to rest more quickly, and the cycle of the operation can be -speeded up somewhat.

Having thus described my invention what I claim is 1. In an automatic temperature regulator for a plurality of electric heaters, a plurality' of thermo-electric elements associated with said heaters, a plurality of circuit controllers for regulating the current supplied to said heaters, a single control instrument adapted to be influenced by one or another of said thermo-electric elements, a common distributor with switches and-connections whereby the Single control instrument is placed in operative relation with one or another of said thermo-electric elements and with the correspondin circuit controllers, and manually control able means forindependently varying the electrical action of each thermoelectric element. 2. In anv automatic temperature regulator for a plurality, of electric heaters, a Aplurality of 'thermo-electric elements. associated with said heaters, a plurality of circuit oontrollers for regulating the current supplied to said heaters, a single control instrument adapted to be influenced by one or another'` of said thermo-electric elements, va common distributorwit'haswltches and connectlons whereby the slngle control instrument 1s placed in operative relation with one or an- HOWARD A. v ANDS. 

